Attachments messed up going to Exchange

[Michael Crider]

We migrated from a hosted mail server to an in-house server one month 
ago, running CentOS 4.4, MailScanner 4.59.4, Postfix 2.2.10, ClamAV and 
SpamAssassin 3.1.7, initially installed from the howto at hughesjr.com, 
then fine tuned with the awesome info in FSL's manual and the mail list 
archives. Today is the first day with a problem that I haven't seen 
covered (may have overlooked). One of our users is trying to send an 
attachment to the USDA. She has tried both xls and pdf files. In both 
cases the person receiving it says he is only getting a .dat file. 
According to his email headers, he is using Exchange 6.0, and our user 
is using Thunderbird 2.0. She can email them to other users without a 
problem (have tested both local users and my home email account). His 
replies have all come back with the original email inline (no headers or 
attachments), so I can't tell where the problem is. She had emailed 
attachments to him as recently as April 3 through the hosted server 
without a problem, but I have no idea how it was configured (I know it 
ran SpamAssassin, but nothing beyond that). Has anyone else seen 
anything like this, or have suggestions on what I should look for? I 
don't know how computer literate he is, so I don't know how much to ask 
him (and Washington DC is a long way from Missouri for me to run over 
and look myself :).

Thanks for any advice.
Michael

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